1. Field of the Invention
This invention relates to an image sensing device which converts the image of an object to be photographed into an electrical signal by means of an image sensor such as an image tube or a charge coupled device (CCD).
2. Description of the Prior Art
In the conventional image sensing devices of the kind using a camera tube or a CCD as an image sensor, the dynamic range of the image sensor is very narrow. The output level of the image sensor, therefore varies to a great extent even for a slight exposure deviation. To electrically correct this variation, an automatic gain control circuit (hereinafter called AGC) has heretofore been arranged to keep the level of a signal which is to be transmitted to a signal processing circuit and a recording circuit nearly constant irrespective of the magnitude of the output of the image sensor. However, in a device of this kind, it is impossible to store exposure information (AE lock) or to correct an exposure for a back-lighted subject because the AGC negates the variations of the output level of the image sensor. Furthermore, conventional devices cannot cope with cases where an exposure condition at the time of photographing changes completely from the previously existing light measurement condition as flash photography.